Two-Ply Paper Sack with Air-Permeable Moisture Barrier Film
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Solution Overview
Problem
Existing sack designs face challenges in achieving high deaeration rates during filling without compromising the water-resistant properties, often requiring complex constructions or perforations that reduce moisture barrier effectiveness.
Innovation Solution
A sack design featuring an inner and outer paper ply with an air-permeable moisture barrier film between them, where the outer ply has a higher expandability parameter than the inner ply, forming an interply space and film-ply deaeration space to enhance air escape during filling, while maintaining moisture barrier integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the moisture barrier is perforated to facilitate deaeration, then air permeability is improved, but water-resistant properties deteriorate
Solution Approach 1:
The moisture barrier film has different properties in different regions: it is impermeable to water throughout, but has localized perforations or slits that are impermeable to water yet permeable to air. This local differentiation allows the barrier to maintain its water-resistant function while providing air escape routes for deaeration during filling.
Solution Approach 2:
The moisture barrier film is designed with a porous structure that allows selective permeability - the porous matrix permits air molecules to pass through while the continuous polymer matrix blocks water molecules. The porosity is controlled to enable deaeration without compromising moisture protection.
2Use of energy by moving object
If the porosity of Kraft paper is increased to facilitate air permeability, then deaeration is improved, but overall strength deteriorates
Solution Approach 1:
The sack wall is constructed as a composite structure combining Kraft paper plies with a moisture barrier film. The Kraft paper provides mechanical strength while the moisture barrier film handles the air permeability function through its controlled porous structure. This functional separation allows each material to optimize its properties without compromising the other.
Solution Approach 2:
Different regions of the sack wall have different functional qualities: the Kraft paper plies provide structural strength throughout, while the moisture barrier film provides localized air permeability through its perforated or slitted design. This local differentiation allows the system to achieve both strength and deaeration capability.
3Reliability
If a moisture barrier is incorporated as an intermediate layer, then protection against moisture penetration is improved, but deaeration during filling deteriorates
Solution Approach 1:
The moisture barrier film is designed with non-uniform properties: it maintains continuous water impermeability while incorporating localized air permeable features such as perforations or slits. This local quality differentiation enables the barrier to simultaneously protect against moisture while allowing air to escape during filling operations.
Solution Approach 2:
The moisture barrier film utilizes a porous polymer structure that enables selective transport - the porous matrix allows air molecules to diffuse through while the continuous film matrix blocks water molecules. This porous design maintains moisture protection while facilitating deaeration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design allows for increased deaeration rates during filling, improving filling efficiency without compromising the water-resistant properties of the sack, as demonstrated by superior air permeability compared to other deaeration concepts.
Implementation Method 1
a parameter of the outer ply relates to the parameter of the inner ply so as to form an interply space between the inner and outer ply if an overpressure is present inside the sack
Implementation Method 2
an air permeable moisture barrier film arranged between the inner ply and the outer ply
Data Source
Figure 1
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AI summary
The invention relates to the field of sacks, and especially to deaeration thereof. A sack (1), wherein at least part of a sack wall of the sack comprises an inner ply (2), an outer ply (3) and an air permeable moisture barrier film (4) arranged between the inner ply (2) and the outer ply (3) is provided. A parameter of the outer ply (3) relates to the parameter of the inner ply (2) so as to form an interply space between the inner and outer ply if an overpressure is present inside the sack. The sack (1) is adapted to form at least one film-ply deaeration space between the moisture barrier film (4) and the outer ply (3) within the at least part of the sack wall if the overpressure is present. Also provided are a sack wall material, a method for deaeration of a sack (1) and a method for manufacturing a sack.